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EXPERIMENT 4
THEVENIN’S & NORTON’S THEOREM AND MAXIMUM POWER
TRANSFER THEOREM
PART A - THEVENIN
1.
2.
Measure the resistance of each resistor. Record these values
in Table 4.1 Select RL as the resistor where it is proposed to
determine the current value
Construct the circuit in Fig 4.1.
Table 4.1
V1
R1
Measured values
R2
R3
R4
R5
RL
3. Remove resistor RL from the network.
4. Turn on the supply. Measure the voltage between the points A and D of the network.
This is the Thevenin’s voltage. Record the value in Table 4.2
Table 4.2
Measured values
Theoretical values
Thevenin’s Thevenin’s current in Thevenin’s Thevenin’s current in
resistance
voltage
RL
resistance
voltage
RL
PART B - NORTON
1. Construct the circuit as shown in Fig. 4.1. Do not turn on the supply
2. Remove resistor RL from the network. RL is selected as the resistor where it is
proposed to determine the current value.
3. Turn on the supply. Read the current shown by the ammeter between terminals
A and D. This is Norton’s current, IN. Record its value in Table 4.3.
Table 4.2
Measured values
Theoretical values
Thevenin’s Thevenin’s current in Thevenin’s Thevenin’s current in
resistance
voltage
RL
resistance
voltage
RL
Table 4.3
Measured values
Norton’s
Norton’s
Resistance
current
current in
RL
Theoretical values
Norton’s
Norton’s
resistance
current
current
in
RL
PART A - THEVENIN
5. Switch off the power supply. Replace the power supply V1 with a short circuit.
6. Measure the resistance between terminals A and D. This is the Thevenin’s resistance.
Record the value in Table 4.2
Table 4.2
Measured values
Theoretical values
Thevenin’s Thevenin’s current in Thevenin’s Thevenin’s current in
resistance
voltage
RL
resistance
voltage
RL
PART B - NORTON
4. Switch off the power supply. Replace the supply with a short circuit.
5. Measure the resistance between terminals A and D. This is Norton’s resistance,
record the value in Table 4.3.
Table 4.2
Measured values
Theoretical values
Thevenin’s Thevenin’s current in Thevenin’s Thevenin’s current in
resistance
voltage
RL
resistance
voltage
RL
Table 4.3
Measured values
Norton’s
Norton’s
Resistance
current
current in
RL
Theoretical values
Norton’s
Norton’s
resistance
current
Conclusion: RTH = RN
current
in
RL
PART A - THEVENIN
7. Place back the resistor RL in circuit with an ammeter is connected between terminals A
and B or C and D.
8. Remove the short circuit connection and place back the supply in the circuit.
9. Turn on the supply. Read and record the current value flowing in the resistor RL.
Table 4.2
Measured values
Theoretical values
Thevenin’s Thevenin’s current in Thevenin’s Thevenin’s current in
resistance
voltage
RL
resistance
voltage
RL
PART B - NORTON
6. Place back the resistance RL in circuit with an ammeter is connected between
terminals A and B or C and D.
7. Place back the power supply in the circuit and remove the short circuit connection.
8. Read and record the current value flowing in the resistor RL.
Table 4.2
Measured values
Theoretical values
Thevenin’s Thevenin’s current in Thevenin’s Thevenin’s current in
resistance
voltage
RL
resistance
voltage
RL
3.2559 V 4.072 mA
619.6 Ω
Table 4.3
Measured values
Norton’s
Norton’s
Resistance
current
current in
RL
Theoretical values
Norton’s
Norton’s
current in
resistance
current
RL
619.6 Ω
5.255 mA
4.072 mA
PART C – MAXIMUM POWER
TRANSFER
1. Set up the circuit as shown in Fig. 4.2.
B
A
I
C
D = GND
2. Apply 10V DC from the DC power supply.  Vth = 10 V
No connection
Connect to DMM
(-ve) = node C
RL
Connect to GND
3.
4.
5.
6.
Use the resistor, Rth = 5kΩ
Vary the load rheostat RL from 0 Ω to 10 kΩ.
Measure the voltages VL and I. Take 11 sets of reading.
Record all result in Table 4.4.
Connect to DMM to
measure the resistance
0kΩ, 1kΩ, 2kΩ, 3kΩ, 4kΩ, 5kΩ, 6kΩ, 7kΩ, 8kΩ, 9kΩ, 10kΩ
No.
VTH
VL (V)
I (mA)
PIN = VTH I
POUT = VL I
Loss = PIN  POUT
%η
1
2
3
4
5
6
10 V
7
8
9
10
11
%η = ( Pout / Pin ) x 100 %
%VR = ( RTH / RL) x 100 %
%VR
RL = VL / I